<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script src="https://cdn.bootcss.com/jquery/3.3.1/jquery.min.js"></script>
</head>
<body>
<style>
    #canvas {
        width: 500px;
        height: 500px;
    }
</style>
<div id="canvas"></div>

<script>
    let c = document.getElementById("canvas");
    let ctx = c.getContext("2d");
    ctx.fillStyle = "#FF0000";
    ctx.fillRect(0, 0, 150, 75);
</script>
</body>
</html>